add configurable support for wrapping any raised Exception in a RetryError instead of just raising it directly, add a few more comments
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56
retrying.py
56
retrying.py
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@ -49,13 +49,16 @@ class Retrying:
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wait_incrementing_start=0, wait_incrementing_increment=100,
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wait_exponential_multiplier=1, wait_exponential_max=sys.maxint,
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retry_on_exception=None,
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retry_on_result=None):
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retry_on_result=None,
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wrap_exception=False):
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# TODO add chaining of stop behaviors
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# stop behavior
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self.stop = getattr(self, stop)
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self._stop_max_attempt_number = stop_max_attempt_number
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self._stop_max_delay = stop_max_delay
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# TODO add chaining of wait behaviors
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# wait behavior
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self.wait = getattr(self, wait)
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self._wait_fixed = wait_fixed
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@ -72,35 +75,44 @@ class Retrying:
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else:
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self._retry_on_exception = retry_on_exception
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# TODO simplify retrying by Exception types
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# retry on result filter
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if retry_on_result is None:
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self._retry_on_result = self.never_reject
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else:
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self._retry_on_result = retry_on_result
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self._wrap_exception = wrap_exception
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def never_stop(self, previous_attempt_number, delay_since_first_attempt_ms):
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"""Never stop retrying."""
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return False
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def stop_after_attempt(self, previous_attempt_number, delay_since_first_attempt_ms):
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"""Stop after the previous attempt >= max attempt number."""
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"""Stop after the previous attempt >= stop_max_attempt_number."""
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return previous_attempt_number >= self._stop_max_attempt_number
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def stop_after_delay(self, previous_attempt_number, delay_since_first_attempt_ms):
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"""Stop after the delay from the first >= max delay."""
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"""Stop after the time from the first attempt >= stop_max_delay."""
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return delay_since_first_attempt_ms >= self._stop_max_delay
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def no_sleep(self, previous_attempt_number, delay_since_first_attempt_ms):
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"""Return 0, don't sleep at all before retrying."""
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"""Don't sleep at all before retrying."""
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return 0
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def fixed_sleep(self, previous_attempt_number, delay_since_first_attempt_ms):
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"""Sleep a fixed amount of time between each retry."""
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return self._wait_fixed
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def random_sleep(self, previous_attempt_number, delay_since_first_attempt_ms):
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"""Sleep a random amount of time between wait_random_min and wait_random_max"""
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return random.randint(self._wait_random_min, self._wait_random_max)
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def incrementing_sleep(self, previous_attempt_number, delay_since_first_attempt_ms):
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"""
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Sleep an incremental amount of time after each attempt, starting at
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wait_incrementing_start and incrementing by wait_incrementing_increment
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"""
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result = self._wait_incrementing_start + (self._wait_incrementing_increment * (previous_attempt_number - 1))
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if result < 0:
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result = 0
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@ -135,16 +147,16 @@ class Retrying:
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attempt_number = 1
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while True:
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try:
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attempt = Attempt(fn(*args, **kwargs), False)
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attempt = Attempt(fn(*args, **kwargs), attempt_number, False)
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except BaseException as e:
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attempt = Attempt(e, True)
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attempt = Attempt(e, attempt_number, True)
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if not self.should_reject(attempt):
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return attempt.get()
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return attempt.get(self._wrap_exception)
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delay_since_first_attempt_ms = int(round(time.time() * 1000)) - start_time
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if self.stop(attempt_number, delay_since_first_attempt_ms):
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raise RetryError(attempt_number, attempt)
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raise RetryError(attempt)
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else:
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sleep = self.wait(attempt_number, delay_since_first_attempt_ms)
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time.sleep(sleep / 1000.0)
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@ -152,22 +164,38 @@ class Retrying:
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attempt_number += 1
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class Attempt:
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"""
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An Attempt encapsulates a call to a target function that may end as a
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normal return value from the function or an Exception depending on what
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occurred during the execution.
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"""
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def __init__(self, value, has_exception):
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def __init__(self, value, attempt_number, has_exception):
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self.value = value
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self.attempt_number = attempt_number
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self.has_exception = has_exception
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def get(self):
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def get(self, wrap_exception=False):
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"""
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Return the return value of this Attempt instance or raise an Exception.
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If wrap_exception is true, this Attempt is wrapped inside of a
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RetryError before being raised.
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"""
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if self.has_exception:
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raise self.value
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if wrap_exception:
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raise RetryError(self)
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else:
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raise self.value
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else:
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return self.value
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class RetryError(Exception):
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"""
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A RetryError encapsulates the last Attempt instance right before giving up.
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"""
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def __init__(self, failed_attempts, last_attempt):
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self.failed_attempts = failed_attempts
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def __init__(self, last_attempt):
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self.last_attempt = last_attempt
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def __str__(self):
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return "Failed attempts: %s, Last attempt: %s" % (str(self.failed_attempts), str(self.last_attempt))
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return "Last attempt: %s" % str(self.last_attempt)
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